Check Required Elements and Attributes in JAXB

[malsh1358]

Hi

I need check required elements and attributes in JAXB java classes , if there are any value for them place it , otherwise place default value in xml file , because of it I upgrade JAXB2.0 to JAXB 2.1 to support "required" in "XmlElement" , I read in "JavaWS(JAXB)Tutorial.pdf" that JAXB itself check required elements and attributes , if there are any value for them place it , otherwise place default value in xml file , the exact part of document is :
<< A property is said to have a set value if that value was assigned to it during unmarshalling or by invoking its mutation method. The value of a property is
its set value, if defined; otherwise, it is the property’s schema specified default value, if any; otherwise, it is the default initial value for the property’s base type as it would be assigned for an uninitialized field within a Java class. >>


I want to know , dose JAXB do this task ? (now I work with JAXB2.1 but it doesnt do this task.Maybe I must set some configuration)
and if JAXB doesnt do it , how I can check required elements and attributes in JAXB ?

Please help me.

Shariat